Ward Swingle, who has died aged 87, first had the idea of singing the works of JS Bach to the scat syllables of jazz in the early 1960s, during a quiet moment as a backing singer for recordings in Paris. The American-born musician – he was also a fine pianist – had been introduced to that world by the French jazz vocalist Christiane Legrand. She subsequently became lead soprano for Les Swingle Singers, the first of his lineups to provide one of the most distinctive sounds in popular music.

The steady tempo of Baroque music lent itself naturally to a rhythmical approach and improvisation. Adding a light accompaniment of bass and drums to his agile vocal team, Ward was able to approach the Philips label with the idea of making a recording, with little expectation that it would be a success. Jazz Sebastian Bach (1963) was taken up by radio stations in the US, resulting in a tour there and the first of Ward’s five Grammies. More international touring followed, with explorations of the works of Mozart, Vivaldi and even Les Romantiques – 19th-century composers from Beethoven to Mussorgsky.

The composer Luciano Berio was a great fan of the Swingle sound, so when Leonard Bernstein commissioned a new piece to celebrate the 125th anniversary of the New York Philharmonic in 1968, he wrote Sinfonia, which had the Swingle Singers’ eight amplified voices not just singing but whispering and shouting a commentary drawn from a variety of texts. In 1969 Berio and the Swingle Singers performed it with the BBC Symphony Orchestra at the Proms.

The English choral tradition had always fascinated Ward, so when the French group disbanded in 1973, he moved his family to Fairwarp, near Uckfield in East Sussex. He wanted to use young classically trained voices for close-mic singing, so that the sound could combine the intimacy and clarity of the spoken word with precise tuning and the iron-clad rhythm and jazz inflections of the French Swingles. He had promised that the new group would not use the same name, so the British group was called Swingle II until 1977-78, and subsequently the New Swingle Singers and the Swingles.

Already a huge fan of the Swingle sound, I was thrilled to be recruited for the new team. Our albums ranged from madrigals to cover versions of the latest hits; big band recreations similar to those of Les Double Six, with whom Ward had sung in Paris; rags by Scott Joplin and jazz numbers by Fats Waller, Jelly Roll Morton and Bix Beiderbecke; and 20th-century French and English part songs. Concert programmes reflected the same eclectic mix, as well as scatted versions of Bach and Handel, and there were TV appearances with such luminaries as the Two Ronnies, Cleo Laine and Shirley Bassey.

When we began to tour regularly in the US it became clear that we could not afford to keep our rhythm section, so the evolution of the group as an a cappella ensemble was born of necessity, but proved to be very exciting. We did, however, still have Ward’s wonderful piano playing to rely on – from the stunning cadenza of Bach’s Fifth Brandenburg Concerto in our early days to the smoky chords of Mood Indigo at the Village Gate in New York. Ward maintained that he always wrote himself a reasonably undemanding second tenor vocal line so that he could keep an ear on what the rest of us were doing. Of the many LP albums with the English line-up that included Ward, only Live in New York (1982) and a compilation called Swing Sing, comprising Rags and All That Jazz and some big band and pop covers, are available on CD.

Our collaboration with Berio continued through many performances of Sinfonia and a recording of the complete five-movement version with Pierre Boulez and the Orchestre National de France (1984). We also recorded Berio’s Cries of London and A-Ronne. By this time Ward had produced more than 200 arrangements and compositions, recorded two dozen albums and given more than 2,000 concerts. In 1984 he retired from performing and moved to New Jersey, but continued to be musical adviser to the group.

Ward Swingle and the Swingle Singers rehearsing Bach’s Badinerie, from the Suite No 2 in B minor for flute and strings, in Michael Lawrence’s film Bach & Friends (2010)

Born in Mobile, Alabama, Ward was the son of Ira and Kathryn (nee Williams). His father, who ran a small electrical contracting business, had wanted to be a musician, and made sure his four children were well taught. Ward and his siblings all played instruments and sang as a vocal group. On the matter of pitch, Ward remembers his father saying: “Here’s an ‘A’. If you don’t remember it you don’t go to the movies on Saturday.”

At the Cincinnati Conservatory, Ohio, Ward studied the piano and met the French violinist Françoise Demorest. They both gained scholarships to study in Paris – Ward with Walter Gieseking and Françoise with Georges Enesco – and married there in 1952.

Ward spent an inordinate amount of time proving that his name really was Swingle. It derived from the Swiss name Zwingli – and it was purely coincidental that Les Swingle Singers became famous for “swinging” the works of JS Bach. On moving to Britain he was further bemused to find that many people thought his first name was Les.

While working as rehearsal pianist with Roland Petit’s Ballet de Paris, Ward had met the composer Michel Legrand. Christiane was Michel’s sister, and through her Ward had joined Blossom Dearie’s group the Blue Stars and subsequently Mimi Perrin’s Les Double Six, with its recreations of numbers by Quincy Jones and Dizzy Gillespie. It was probably the experience of singing instrumental parts in these jazz classics that led to the idea of doing the same with classical instrumental music.

After his return to the US, Ward lectured, gave masterclasses all over the world, worked with established groups such as the Stockholm Chamber Choir, and published his arrangements. The Swingles have continued to evolve, celebrating a 50th anniversary in 2013 and creating and curating the annual London A Cappella Festival at Kings Place in the north of the city.

In 1994 Ward and Françoise moved to Fère-en-Tardenois, north-east of Paris, and in 2004 Ward was appointed Officier de l’Ordre des Arts et des Lettres. Last December they returned to England to live with their daughter Rebecca.

Ward is survived by Françoise, Rebecca, their two other daughters, Kathryn and Elizabeth, and his grandchildren Patrick, Emma and Isabella.